1948: Harry Truman’s Improbable Victory and the Year that Transformed America, by David Pietrusza

Everyone has seen the hilarious photo of a victorious President Truman holding up the “DEWEY DEFEATS TRUMAN” headline, but what makes the election of 1948 so important today is the reason behind that photo: the disastrously bad polling that had Dewey pegged as a shoe-in for victory. Understanding not just the failure of early polling techniques, but the way a long-shot candidate like Truman pulled together the support necessary for victory, is crucial to understanding every election held since.